Logic gate realised from pn Junctions shown in figure is

Options

A. OR gate
B. AND gate
C. NOT gate
D. NOR gate

Answer

To determine the type of logic gate realized from the given PN junctions in the circuit, we will analyze the behavior of the diodes based on the inputs A and B.

### Step-by-Step Solution:

1. **Identify the Components**:
- The circuit consists of two diodes (D1 and D2) connected to points A and B, and the output is taken from point Y, which is connected to a resistor that goes to the ground.

2. **Analyze the Input Conditions**:
- We will evaluate the output Y for all possible combinations of inputs A and B (0 and 1).

3. **Case 1: A = 0, B = 0**:
- Both diodes D1 and D2 are reverse-biased (since both inputs are 0).
- Therefore, no current flows, and the output Y = 0.

4. **Case 2: A = 0, B = 1**:
- D1 is reverse-biased (0V), and D2 is forward-biased (1V).
- D2 conducts, allowing current to flow, hence the output Y = 1.

5. **Case 3: A = 1, B = 0**:
- D1 is forward-biased (1V), and D2 is reverse-biased (0V).
- D1 conducts, allowing current to flow, hence the output Y = 1.

6. **Case 4: A = 1, B = 1**:
- Both D1 and D2 are forward-biased.
- Both diodes conduct, allowing current to flow, hence the output Y = 1.

7. **Construct the Truth Table**:
- Based on the evaluations above, we can summarize the results in a truth table:

| A | B | Output Y |
|---|---|----------|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |

8. **Determine the Logic Gate**:
- From the truth table, we can see that the output Y is 1 when at least one of the inputs (A or B) is 1. This behavior corresponds to the OR logic gate.

### Conclusion:
The logic gate realized from the PN junctions shown in the figure is an **OR gate**.